Diazotype transfer developing method



Aug. 31, 1965 P. MULLER 3,203,798

DIAZOTYPE TRANSFER DEVELOPING METHOD Filed NOV. 28, 1962 ,wsrf/iL EfUnited States Patent O 3,203,798 DIAZTYPE TRANSFER DEVELOPING METHODPeter Muller, Port Washington, NSY., assigner to Andrews Paper &'Chemical Co., Inc., Great Neck, NX., a corporation of New York FiledNov. 28, 1962, Ser. No. 240,575 2 Claims. (Cl. 96-49) This inventionrelates to an improved diazotype transfer developing method and to animproved developer sheet for use in such method.

The diazotype reproduction process is based on the sensitivity of thediazo compounds to the short Wave length portion of the visible spectrumand to ultraviolet light and also on the capacity of diazo compounds toreact with certain compounds generally called couplers to form azo dyesunder controlled pH conditions.

Diazotype light sensitive material are available in two general forms:

(l) The two component or dry system in which the backing sheet has adiazo sensitized coating or coatings is exposed to actinic radiationbehind the master which is to be reproduced and thereafter the exposeddiazo sensitized sheet is exposed to aqueous ammonia vapor which inducethe development of the azo dye in the areas which have not been exposedto light.

(2) The single component or semi-moist system in which the backing sheethas a diazo sensitized coating is exposed to light behind a master,thereafter diazo reproduction sheet is moistened with an aqueoussolution containing a dye forming coupler and other compounds therebyinducing the development of an azo dye in the areas which have not beenexposed to light.

Both of these systems have certain recognized dithculties anddisadvantages. Thus, in the iirst or two component system, difficulty isencountered with the arnmonia vapors which must be exhausted so as notto annoy and inconvenience the persons present in the printing room.This problem is particularly aggravated in the case of air-conditionedbuildings where the ammonia is drawn into the recirculated air. Thesecond or single component system involves the inconvenience of handlingand disposing of developing liquids which are particularly troublesomeand annoying in business oflices.

Attempts have been made to overcome these difficulties and disadvantagesby completely dry development methods, such as the thermal developmentmethods. The thermal development methods heretofore attempted fall intothree general classification:

(1) Single sheet processes which contain in the sheet a light sensitivediazo compound at least one coupler and a stabilizing substance whichprevent azo dye formation under ordinary temperatures and conditions,but which permit 'dye formation under the elevated temperaturesencountered in the thermal development equipment. In methods of thistype the diazo material generally has insuicient sheli:` life, or ifthey are adequately stabilized, require excessively high temperaturesand prolonged exposures thereto with detrimental eifect on the dye andoccasional charring of the paper backing. ln addition, such methods failto provide the desired density of color. Furthermore, difficulty isencountered in providing the moisture required for development.

(2) Double sheet process using one light sensitive sheet containing thediazo compound and a second sheet containing a dye forming coupler andat least another substance of an alkaline character. The sheets arebrought into close contact with each other under elevated temperaturecontrolled conditions to cause transfer of the dye forming coupler tothe light sensitive sheet. The double hjg Patented Aug. 3l, 1965 sheetprocess has not been generally successful because of the slow mobilityand low volatility of adequate dye forming couplers under conditionswhich are not detrimental to the dye formed therefrom or the papermaterial.

(3) Developer sheet process using one light sensitive sheet containingthe diazo compound, a dye forming coupier and a stabilizer and adeveloper sheet which contains the developing agents and transfers themto the light sensitive sheet under proper thermal conditions. Thedeveloper sheet processes heretofore available have been of loweiiiciency. Frequently very high developing temperatures were needed andthe Water was driven off before the ammonia was generated and was ableto enter the light sensitive layer to create the proper pH conditions.In other instances using lower developing temperatures, the ammonia wasreleased prematurely at room temperature resulting in a short shelf lifeand also causing the same inconvenient smell associated with the twocomponent ammonia system.

lt is a particular object of the present invention to overcome thedifiiculties and disadvantages heretofore encountered and to provide animproved diazotype transfer developing method and developer sheet foruse therein in which high rate of synchronized development and printingis maintained; in which the development takes place at moderatetemperatures in a reasonable period of time so that no damage is causedto the dyes or backing sheets; and which produces prints of verysatisfactory dye density and intensity.

A further object of my invention is to provide a developing method fordeveloping a diazo print using a standard type of machine as forinstance a conventional and widely existing ammonia diazotype processingmachine, without the objectionable use of aqueous ammonia vaporstherein.

My improved method presents the further advantages that it may utilizestandard diazo reproduction sheets used in the two component ammoniasystem. It presents a further advantage that it utilizes the developersheet which is dry, which is not light sensitive, which has anindefinite shelf life, which does not generate adverse odors whensubjected to heat, and which may be used one or more times fordeveloping a sensitized diazo reproduction sheet.

In my copending application Serial No. 230,850, tiled Gctober 16, 1962briefly stated, l provide a developer sheet for the thermal developmentof diazo sensitized prints. The diazo sensitized sheet is superimposedon a developer sheet constaining an organic amine, that is non-volatiieat normal ambient temperatures and atmospheric conditions and a sourceof water that may take the form of crystals having water ofcrystallization combined therewith. Subjecting the superimposed sheetsto elevated temperatures, the organic amine volatilizes and the water isreleased mixing with the sensitized layer of the reproduction sheet andraising the pH level to permit the coupler to combine with the diazocompound to form an azo dye.

My invention contemplates in addition to the use of a eveloper sheetcontaining an organic amine which is non-volatile at normal ambienttemperatures and atmospheric conditions, an improved developing methodfor developing a print on a diazo reproduction sheet which comprisessubjecting the diazo reproduction sheet to actinic radiation behind amaster, superimposing the developer sheet and the exposed diazoreproduction sheet and exposing both to an atmosphere containing watervapor at elevated temperatures so that the organic amine and watervapors penetrate the diazo sensitized coating to cause the couplingcompound contained in the diazo reproduction sheet to couple with thediazo compound therein and thereby develop the image in the unexposedportion of the diazo reproduction sheet.

In a preferred form, my invention contemplates arranging in superimposedrelationship an exposed diazo reproduction sheet and a developer sheetcontaining an organic amine which has a low vapor pressure and issubstantially non-volatile at ambient temperatures and subjecting thesuperimposed sheets to an atmosphere containing steam which volatilizesthe organic amine so that both the organic amine and steam induce thedevelopment of the diazo compound with the coupler in the sensitizedlayer of the reproduction sheet to form an azo dye.

In the accompanying drawing:

FIG. 1 is a perspective View of a developer sheet embodying myinvention;

FIG. 2 is a diagrammatic view showing a master superimposed upon a diazoreproduction sheet and exposed to light; and

FIG. 3 is a diagrammatic view showing the exposed diazo reproductionsheet superimposed on the developer sheet exposed to a water vaporgenerator.

For a more detailed description of my improved diazo developing methodreference is made to the accompanying drawings.

In FIG. 1 I show my developer sheet comprising a suitable backing sheetas shown, made of suitable material that is permeable to water vapors,such as paper, ber board or plastic, which is inert to the coatingmaterials applied thereto and also to the materials in the diazosensitized layer of the reproduction sheet. The backing sheet shouldeither be sufciently absorbent to be partially impregnated with thecoating materials, or if it is not absorbent, it should have surfacecharacteristics of a type that the coating materials will adherethereto. For the backing sheet I have found that various types of paper,such as kraft paper, serve very satisfactorily.

I apply a developer coating embodying my invention to one or both of thesurfaces and the backing sheet, and, as previously indicated, it may beat least partially absorbed therein. The developer coating includes anorganic amine which has low vapor pressure at ordinary ambienttemperatures, such as room temperature or temperatures lower than 100C., but which is sufficiently volatile and will volatilize attemperatures between 100 and 180 C., and which will volatilize in thepresence of water vapor at temperatures between 70 to 180 C. The amineselected should also be of a type which has no undesired effect on thediazo and coupling compounds in the sensitized layer of the reproductionsheet during the development period. Representative amines which may beused for this purpose are piperazine, t-butylamineethanol,t-butyl-diethanolamine, diethanolamine, aminoethylethanolamine, methanediamine, aminoethyl-piperazine, 1,2,ll-trimethylpiperazine,2,6-dimethyl-morpholine, and triethanolamine. The organic amine used maybe ether in solid crystalline form, such as piperazine ortbutylamine-ethanol, or may be a liquid such as 2,6-dimethyl-morpholine.However, the organic amine used should be one in which it issubstantially non-volatile at ambient temperatures and which is volatileat between 100-180 C., and which will volatilize in the presence ofwater vapor at temperatures between 70-180 C. I prefer to use piperazinewhich gives very satisfactory results.

I have found that the developer sheet suitable for the thermaldevelopment method as disclosed in my copending application Serial No.230,850, tiled October 16, 1962, serves very satisfactorily for use indeveloping diazo prints in my present invention. However, I have foundthat very satisfactory prints are also obtained when the crystallinesalts are not employed in the developer coating.

As indicated above, I may include in the developer sheet as a componentin the developer or coating a reservoir of water which under normalambient temperatures is retained in combined dry form but which isreleased when subjected to temperatures in excess of C. For this purposeI have found that crystalline salts having water of crystallizationcombined therewith serve very satisfactorily. Examples of such salts aresodium acetate, sodium thiosulfate, sodium carbonate, sodium sulfate,magnesium sulfate, magnesium chloride and piperazine. Piperazine, whenmixed with water becomes hydrated with the addition of six molecules ofwater to the piperazine molecule and when subjected to developmenttemperature, the water is released; thus serves the double function ofan amine and as a crystalline salt as a reservoir for water. Thecrystalline salts should preferably be selected and mixed together so asto provide a pH, close to neutral. I have found that undesirable resultsare obtained if the coating contains strongr non-volatile alkalies oracids. Thus, if the coating is highly alkaline, the amine is prematurelyreleased. If the coating is excessively acid, the release orvolatilization of the amine is delayed or retarded. I also prefer toinclude an acetate salt as I have found that this serves to neutralizeany trace of odor from the amine.

Under certain circumstances the crystalline salts may be omitted fromthe developer coating and the water supplied from other sources, such aswater absorbed in the backing sheet or from a water vapor generator inthe developing apparatus.

The developer coating also may include suitable binders and adhesives,such as polyvinyl acetate, casein, or the like. Additionally, itpreferably includes dispersing agents, such as finely milled silica,titanium oxide, clay, starch grains or absorptive materials likeactivated carbon or diatomaceous earth or plasticizers such as urea.

The developer coating may be applied to the backing sheet in aqueoussolution or dispersion by conventional diazotype coating equipment.

The proportions and quantities of materials applied t0 the backing sheetmay be varied. I have found that satisfactory results are obtained ifbetween 0.4 and 5.0 grams of organic amine and between 0.5 and 7.0 gramsof crystalline salt having combined water of crystallization per squaremeter are applied to the backing sheet. Dispersing pigments in suchconcentrations as to yield coating weights of 0.5 to 5 grams per squaremeter and binders or adhesives in the amount of from 10 to 100% inproportion to the organic amine have proved advantageous.

After the developer coating has been applied to the backing sheet, thecoating may be suitably dried as in a high velocity air dryer atelevated temperatures but below 100 C.

Optionally, the opposite surface of the backing sheet may have appliedthereto a coating containing some of the water reservoir material or acoating identical to the one on the front side. This coating maycomprise one or more of the `indicated crystalline salts applied inaqueous solution by means of simple diazotype coating equipment. If anoptional coating of this type is applied, satisfactory results areobtained if between 0.5 and 6.0 grams per square meter are applied tothe opposite surface of the backing sheet. After the second coating isapplied, it may be simply dried as in a high velocity air dryer at atemperature below 100 C.

Developer sheet material thus prepared may be cut into individual sheetsof a size to register with diazotype reproduction sheets with which itis to be used. If preferred, the developer sheet material may besupplied in roll form for use in a developing machine in which case theweb of developer material is brought into contact with the exposeddiazotype reproduction sheets of the developing machine.

One of the advantages of my improved developer sheet is that it may beused for developing images on conventional diazo developing equipment ofthe two component type, in which water replaces the aqueous ammonia thatwas heretofore necessary to develop a diazo print in such machines.Typical diazo reproduction sheets of this type are formed of a backingsheet having a sensitized layer applied therto, as shown in FIG. 2.

The sensitized layer includes a diazo compound, a coupling compound andan acidic stabilizing material. Representative diazo compounds used insuch reproduction sheets are as follows: diazo of p-amino-diphenylamine,diazo of p-amino-dimethylaniline, diazo of pamino-diethylaniline, diazoof p-amino-N-ethyl-N-hydroxy-ethyl-aniline, diazo ofp-niorpholino-aniline and diazo of 4-morpholino-2,5diethoxylaniline.Representative couplers used are as follows: resorcinol,2,3-dihydroxynaphtalene, 2,3-dihydroxynaphtalene--sulfonic acid sodiumsalt, acetoacetanilide, 6,7-dihydroxy-2,3disulfonic acid sodium salt.Representative acidic stabilizers are as follows: citric acid, tartaricacid, maleic acid, boric acid, sulfamic acid, and zinc chloride. Othernormal additions to sensitized layers may also be used, like thiourea,hydroxylethyl-allyl-thiorea, magnesium chloride and 1,3,G-naphthalene-trisulfonic acid, sodium salt. `For the purposes of myimproved process, it is preferable that the diazo sensitized layer alsoincludes a hygroscopic agent, such as glycerine, gylcol or a polyglycolas this favors and accelerates the development process. It has beenobserved that when such agents are incorporated in the coating layer ofthe developer sheet, the rate of development is adversely effected.However, when incorporated in the sensitized layer of the diazoreproduction sheet beneficial results are obtained.

In carrying out my improved developing method for developing a print ona diazo sensitized sheet as shown in FIGS. 2 and 3, the master which isto be reproduced is superimposed on the diazo reproduction sheet in theusual manner and is exposed to actinic radiation of the type to whichthe diazo material is sensitive (usually ultra-violet light or low wavelength visible light) in the manner indicated in FIG. 2. The diazomaterial in the exposed portions of the sensitized layer is decomposedby the actinic radiation while the diazo m-aterial protected by theopaque portions of the master remains unaffected. The diazo reproductionsheet is then arranged in superimposed relationship with the developersheet with the sensitive layer of a reproduction sheet in contact withthe developer sheet. The superimposed sheets are then subjected to waterva-por from a water vapor generator below the superimposed sheets in themanner indicated in FIG. 3. The water vapor elevates the temperature ofthe superimposed sheets Within the indicated temperature range ofbetween 70 and 180 C. preferably approximately 100 C. The water vaporvolatilizes the organic amine by a transfer of the heat energy containedin the water vapor. Subsequently, a portion of the water vapor passesthrough the developer sheet in suticient quantity which is transferredtogether with the organic amine to the sensitized coating of thereproduction sheet causing the undecomposed diazo material to combinewith the coupling compound forming an azo dye i1 the unexposed portionsof the reproduction sheet and thereby develop the image.

For the purpose of my invention herein the term steam is defined aswater vapor or water in its vgaseous state. I have found that thedevelopment rate obtained varies depending upon several factors and istherefore a function of the following factors: the vapor pressure of theorganic amine, the temperature of the water vapor, the permeability ofthe backing sheet, and whether a crystalline salt is employed. All ofthese factors affect the development rate and must be taken intoconsideration in setting the time 4for development. I have obtainedrates varying from approximately 21/2 seconds to 30 seconds when thewater vapor temperature is in excess of 70 C. and preferably between 70to 180 C.

Example 1 On a conventional diazotype coating machine, a black kraftpaper of 20 pound basis weight is coated on a kiss 6 roller airknifecoating station, at a coating speed of 2,000 yards per hour with thefollowing preparation:

The coated sheet is dried in a high velocity air dryer at .a temperatureof 70 C. and then the backside of the lsheet is coated in the samemachine in one and the same pass and on an identical coating stationwith the following solution of:

Water cc 650 Sodium thiosulfate (anhydrous) g 350 The sheet is iinallydried under the same conditions as after the first coating. The sheetthus prepared is ready for use as developer sheet. The developer sheetthus prepared may be :cut into individual sheets corresponding in sizeto the diazo reproduction sheets with which they are to 'oe used or maybe supplied in roll form.

In using the developer sheets a diazo reproduction sheet of the twocomponent type suitable for ammonia development as indicated on pages 10and 11 such as those commercially available under the names SOLAR 4101:or Ozalid 200 SS, is exposed to actinic radiation with the mastersuperimposed thereon in a conventional ammonia diazotype processingmachine, for example, Ozamatic machine. The exposed reproduction sheetis then arranged in superimposed relationship with the developer sheetwith the sensitized coating in contact with the developer coating. Bothsheets while in superimposed relationship are passed through thedeveloper section of a conventional type ammonia diazo developingmachine, for example,

Ozarnatic machine, and subjected to steam instead of the usual aqueousammonia vapors. The temperature of the developer section is adjusted toapproximately 100 C. The stream volatilizes the organic amine, and istransferred together with steam passing through the developer sheet tothe diazo sensitized reproduction sheet. The coupling compound combineswith the diazo compound in the unexposed portions of the sensitizedlayer of the reproduction sheet forming an azo dye, producing an imagein a clear vigorous blueline. The prints that are obtained are of highlysatisfactory commercial quality as compared with prints obtained fromthe same diazo reproduction sheet developed in a conventional ammonia`development process.

Example 2 On a conventional diazotype coating machine, a white sull-ite,rosin sized, paper of 20 pound basis weight is coated on a kiss rollerairknife coating station, at a coating speed of 2,400 yards per hourwith the following preparation:

Water cc 650 Sodium acetate (anhydrous) g-- 130 Sodium thiosulfate(anhydrous) g 45 Piperazine (anhydrous) g-- 45 Non-colloidal silicapowder (Davison) .g 45 Non-ionic polyvinyl-acetate dispersion g 65 Thecoated sheet is dried in a convection air dryer at` a temperature of C.and then the backside of the sheet is coated on the same machine and onan identical coating station with the following solution of:

Water cc 900 Sodium sulfate (anhydrous) -g-- The sheet is finally driedunder the same conditions as after the rst coating. The sheet thusprepared is ready for use as developer sheet.

In using the developer sheet for transfer development for diazotypereproductions the same procedure is followed as described in Example 1.

'Z Example 3 On a conventional diazotype coating machine, a white sulte,rosin sized, paper of 20 pounds basis weight is coated on a kiss rollerairknife coating station, at a coating speed of 2,400 yards per hourwith the following preparation:

Water cc 650 Piperazine (anhydrous) g 45 Urea g 60 Non-colloidal silicapowder (Davison) g 45 Non-ionic polyvinyl-acetate dispersion g 65 Thecoated sheet is dried in a convection air dryer at a temperature at 85C. and then the backside of the sheet is `coated on the same machine andon an identical coating station with the following solution of:

Water cc 900 Sodium sulfate (anhydrous) g 100 Example 4 On aconventional diazotype coating machine, a kraft paper of 40 pound basisweight is coated on a kiss roller airknife coating station at a coatingspeed of 2,000 yards per hour with the following preparation:

Water cc 67 0 Sodium acetate (anhydrous) g 80 Sodium thiosulfate(anhydrous) g 50 t-Butyl-amino-ethanol g 50 Non-colloidal silica powder(Davison) g 50 Non-ionic polyvinyl-acetate dispersion g 100 The coatedsheet is dried in a convection air dryer as a temperature of 70 C. andthen the backside of the sheet is coated on the same machine land on anidentical coating station with the following solution of Water cc 900Sodium acetate (anhydrous) g-- 100 Example 5 On a conventional diazotypecoating machine, a kraft paper of 40 pound basis weight is coated on akiss roller airknife coating station at a coating speed of 2,000 yardsper hour with the following preparation:

Water cc-- 670 t-Butyl-amino-ethanol g 50 Non-colloidal silica powder(Davison) g-- 50 Non-ionic polyvinyl-acetate dispersion g 100 The coatedsheet is dried in a convection air dryer at a temperature of 70 C., andthen the backside of the sheet is coated on the same machine and on anidentical coating station with the following solution of Water cc 900Sodium acetate (anhydrous) g 100 The sheet is finally dried under thesame conditions as after the first coating. The sheet thus prepared isready for use as developer sheet.

In using the developer sheet for transfer development for diazotypereproductions the same procedure is followed as described in Example 1.

In the examples given above any of the other indicated organic aminesmay be used and any of the other crystalline salts may be substitutedfor those listed in the examples or may be eliminated therefrom. Also,it will be appreciated that the proportions may be varied within theindicated limits.

It will be seen that I have provided an improved diazotype transferdeveloping method printing process and an improved developer sheet foruse therein in which the shelf life of the print sheet is not affected;in which the development takes place at moderate temperatures within areasonable period of time without damage to the dyes or backing sheet;and which produces prints of very satisfactory dye contrast, intensityand density.

Modifications may be made in the illustrated drawing and exampleswithout departing from the spirit and scope of my invention as definedin the appended claims.

I claim:

1. A developing method for developing a print on a diazo sensitizedsheet of the type having a sensitized coating containing a diazocompound and a coupling compound and which has been previously exposedto actinic radiation behind a master, said developing method comprisingplacing in superimposed relationship the said exposed diazo sensitizedsheet and a developer sheet containing piperazine which is non-volatileat normal ambient temperatures and atmospheric conditions and whichvolatilizes when subjected to an atmosphere containing steam attemperatures in excess of 70 C. and then generating steam exteriorly ofsaid superimposed sheets and passing the steam through said developersheet to the diazo sensitized sheet at a temperature in excess of 70 C.to volatilize said piperazine and so that said volatilized piperazineand steam penetrate the diazo sensitized coating to cause said couplingcompound to couple with the diazo compound in the unexposed portion ofthe diazo reproduction sheet and thereby develop the image.

2. A developing method for developing a print on a diazo sensitizedsheet as set forth in claim 1 wherein a hygroscopic agent isincorporated in the diazo sensitized coating of the diazo sheet.

References Cited by the Examiner UNITED STATES PATENTS 1,906,240 5/ 33Schmidt et al. 96-49 2,172,783 9/39 Alink et al 96-91 XR 2,308,058 1/43Crowley et al. 96-49 2,583,678 1/52 Wilde. 2,691,587 10/54 Grieg 96-492,732,294 1/ 56 Morrison 96--49 2,774,669 12/56 Marron et al. 96--493,046,128 7/62 Klimkowski et al. 96-49 3,076,707 2/ 63 Lawton et al96--49 XR FOREIGN PATENTS 816,601 7/ 59 Great Britain. 1,249,913 11/60France.

OTHER REFERENCES Kosar: Photographic Science and Engineering, vol. 5,No. 4, July-August, 1961, pp. 239-243.

NORMAN G. TORCHIN, Primary Examiner.

1. A DEVELOPING METHOD FOR DEVELOPING A PRINT ON A DIAZO SENSITIZEDSHEET OF THE TYPE HAVING A SENSITIZED COATING CONTAINING A DIAZOCOMPOUND AND A COUPLING COMPOUND AND WHICH AHS BEEN PREVIOUSLY EXPOSEDTO ACTINIC RADIATION BEHIND A MASTER, SAID DEVELOPING METHOD COMPRISINGPLACING IN SUPERIMPOSED RELATIONSHIP THE SAID EXPOSED DIAZO SENSITIZEDSHEET AND A DEVELOPER SHEET CONTAINING PIPERAZINE WHICH IS NON-VOLATILEAT NORMAL AMBIENT TEMPERATURES AND ATMOSPHERIC CONDITIONS AND WHICHVOLATILIZES WHEN SUBJECTED TO AN ATMOSPHERE CONTAINING STEAM ATTEMPERATURES IN EXCESS OF 70*C. AND THEN GENERATING STEAM EXTERIORLY OFSAID SUPERIMPOSED SHEETS AND PASSING THE STEAM THROUGH SAID DEVELOPERSHEET TO THE DIAZO SENSITIZED SHEET AT A TEMPERATURE IN EXCESS OF 70*C.TO VOLATILIZE SAID PIPERAZINE AND SO THAT SAID VOLATILIZED PIPERAZINEAND STEAM PENETRATE THE DIAZO SENSITIZED COATING TO CAUSE SAID COUPLINGCOMPOUND TO COUPLE WITH THE DIAZO COMPOUND IN THE UNEXPOSED PORTION OFTHE DIAZO REPRODUCTION SHEET AND THEREBY DEVELOP THE IMAGE.